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Chemosensors
Volume 12
Issue 7
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Chemosensors, Volume 12, Issue 7 (July 2024) – 28 articles

Cover Story (view full-size image): This study introduces a modular microflow injection analysis (micro-FIA) system based on 3D-printed microfluidic platforms for real-time, online monitoring of Cu(II) in bioleaching processes from e-waste residues. The micro-FIA system incorporates a novel Tesla valve, replacing traditional solenoid valves to enhance durability and reduce maintenance. It accurately determines Cu(II) across a wide concentration range (34-2000 mg L−1) with a low detection limit (9 mg L−1). Our results demonstrate high precision, reproducibility, and applicability to real samples with complex matrices, offering significant cost and efficiency advantages over conventional methods. View this paper
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25 pages, 3884 KiB  
Review
Integrated Photonic Sensors for the Detection of Toxic Gasses—A Review
by Muhammad A. Butt and Ryszard Piramidowicz
Chemosensors 2024, 12(7), 143; https://doi.org/10.3390/chemosensors12070143 - 18 Jul 2024
Viewed by 872
Abstract
Gas sensing is crucial for detecting hazardous gasses in industrial environments, ensuring safety and preventing accidents. Additionally, it plays a vital role in environmental monitoring and control, helping to mitigate pollution and protect public health. Integrated photonic gas sensors are important due to [...] Read more.
Gas sensing is crucial for detecting hazardous gasses in industrial environments, ensuring safety and preventing accidents. Additionally, it plays a vital role in environmental monitoring and control, helping to mitigate pollution and protect public health. Integrated photonic gas sensors are important due to their high sensitivity, rapid response time, and compact size, enabling precise recognition of gas concentrations in real-time. These sensors leverage photonic technologies, such as waveguides and resonators, to enhance performance over traditional gas sensors. Advancements in materials and fabrication techniques could further improve their efficiency, making them invaluable for environmental monitoring, industrial safety, and healthcare diagnostics. In this review, we delved into photonic gas sensors that operate based on the principles of evanescent field absorption (EFA) and wavelength interrogation methods. These advanced sensing mechanisms allow for highly sensitive and selective gas detection, leveraging the interplay of light with gas molecules to produce precise measurements. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes, 2nd Edition)
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13 pages, 3119 KiB  
Article
Plasmonic Optical Fiber Sensors and Molecularly Imprinted Polymers for Glyphosate Detection at an Ultra-Wide Range
by Luca Pasquale Renzullo, Ines Tavoletta, Giancarla Alberti, Luigi Zeni, Maria Pesavento and Nunzio Cennamo
Chemosensors 2024, 12(7), 142; https://doi.org/10.3390/chemosensors12070142 - 17 Jul 2024
Viewed by 708
Abstract
In this study, a surface plasmon resonance (SPR) sensor based on modified plastic optical fibers (POFs) was combined with a specific molecularly imprinted polymer (MIP), used as a synthetic receptor, for glyphosate (GLY) determination in aqueous solutions. Since GLY is a non-selective herbicide [...] Read more.
In this study, a surface plasmon resonance (SPR) sensor based on modified plastic optical fibers (POFs) was combined with a specific molecularly imprinted polymer (MIP), used as a synthetic receptor, for glyphosate (GLY) determination in aqueous solutions. Since GLY is a non-selective herbicide associated with severe environmental and health problems, detecting glyphosate in environmental and biological samples remains challenging. The selective interaction between the MIP layer and GLY is monitored by exploiting the SPR phenomenon at the POF’s gold surface. Experimental results show that in about ten minutes and by dropping microliter volume samples, the presented optical–chemical sensor can quantify up to three orders of magnitude of GLY concentrations, from nanomolar to micromolar, due to a thin MIP layer over the SPR surface. The developed optical–chemical sensor presents a detection limit of about 1 nM and can be used for onsite GLY measurements. Moreover, the experimental analysis demonstrated the high selectivity of the proposed POF-based chemical sensor. Full article
(This article belongs to the Special Issue Recent Advances and Tendencies on High Sensitive Fiber Optic Chemical Sensors and Biosensors)
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28 pages, 10093 KiB  
Review
Recent Developments in Small-Molecule Fluorescent Probes for Cellular Senescence
by Junyoung Park, Youngjun Lee and Jongmin Park
Chemosensors 2024, 12(7), 141; https://doi.org/10.3390/chemosensors12070141 - 15 Jul 2024
Viewed by 918
Abstract
Cellular senescence is a recently emerged research topic in modern biology. Often described as a double-edged sword, it encompasses numerous essential biological processes, including beneficial effects such as wound healing and embryonic development, as well as detrimental contributions to chronic inflammation and tumor [...] Read more.
Cellular senescence is a recently emerged research topic in modern biology. Often described as a double-edged sword, it encompasses numerous essential biological processes, including beneficial effects such as wound healing and embryonic development, as well as detrimental contributions to chronic inflammation and tumor development. Consequently, there is an increasing need to unravel the intricate networks of senescence and develop reliable detection methods to distinguish it from related phenomena. To address these challenges, a variety of detection methods have been developed. In particular, small-molecule fluorescent probes offer distinct advantages such as suitability for real-time live cell monitoring and in vivo imaging, superior tunable properties, and versatile applications. In this review, we explored recent advancements in the development of small-molecule fluorescent probes toward monitoring cellular senescence by targeting various senescence-related biological phenomena. These phenomena include the upregulation of senescence-associated enzymes, perturbation of the subcellular environment, and increased endogenous ROS levels. Moreover, multi-senescence biomarker-targeting approaches are also discussed to improve their sensitivities and specificities for the detection of cellular senescence. With recent advances in senescence probe development, current challenges in this field are also discussed to facilitate further progress. Full article
(This article belongs to the Special Issue A Theme Issue in Honor of Dr. Richard Horobin—Cell or Organelle Selective Fluorescent Probes: Their Design, Mechanism, Modeling and Application)
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37 pages, 22751 KiB  
Review
Machine Learning-Assisted Raman Spectroscopy and SERS for Bacterial Pathogen Detection: Clinical, Food Safety, and Environmental Applications
by Md Hasan-Ur Rahman, Rabbi Sikder, Manoj Tripathi, Mahzuzah Zahan, Tao Ye, Etienne Gnimpieba Z., Bharat K. Jasthi, Alan B. Dalton and Venkataramana Gadhamshetty
Chemosensors 2024, 12(7), 140; https://doi.org/10.3390/chemosensors12070140 - 15 Jul 2024
Cited by 1 | Viewed by 1561
Abstract
Detecting pathogenic bacteria and their phenotypes including microbial resistance is crucial for preventing infection, ensuring food safety, and promoting environmental protection. Raman spectroscopy offers rapid, seamless, and label-free identification, rendering it superior to gold-standard detection techniques such as culture-based assays and polymerase chain [...] Read more.
Detecting pathogenic bacteria and their phenotypes including microbial resistance is crucial for preventing infection, ensuring food safety, and promoting environmental protection. Raman spectroscopy offers rapid, seamless, and label-free identification, rendering it superior to gold-standard detection techniques such as culture-based assays and polymerase chain reactions. However, its practical adoption is hindered by issues related to weak signals, complex spectra, limited datasets, and a lack of adaptability for detection and characterization of bacterial pathogens. This review focuses on addressing these issues with recent Raman spectroscopy breakthroughs enabled by machine learning (ML), particularly deep learning methods. Given the regulatory requirements, consumer demand for safe food products, and growing awareness of risks with environmental pathogens, this study emphasizes addressing pathogen detection in clinical, food safety, and environmental settings. Here, we highlight the use of convolutional neural networks for analyzing complex clinical data and surface enhanced Raman spectroscopy for sensitizing early and rapid detection of pathogens and analyzing food safety and potential environmental risks. Deep learning methods can tackle issues with the lack of adequate Raman datasets and adaptability across diverse bacterial samples. We highlight pending issues and future research directions needed for accelerating real-world impacts of ML-enabled Raman diagnostics for rapid and accurate diagnosis and surveillance of pathogens across critical fields. Full article
(This article belongs to the Special Issue Artificial Intelligence (AI)/Machine Learning (ML)-Assisted Chemical Sensors)
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11 pages, 1904 KiB  
Article
A Novel Electronic Nose Using Biomimetic Spiking Neural Network for Mixed Gas Recognition
by Yingying Xue, Shimeng Mou, Changming Chen, Weijie Yu, Hao Wan, Liujing Zhuang and Ping Wang
Chemosensors 2024, 12(7), 139; https://doi.org/10.3390/chemosensors12070139 - 14 Jul 2024
Viewed by 810
Abstract
Odors existing in natural environment are typically mixtures of a large variety of chemical compounds in specific proportions. It is a challenging task for an electronic nose to recognize the gas mixtures. Most current research is based on the overall response of sensors [...] Read more.
Odors existing in natural environment are typically mixtures of a large variety of chemical compounds in specific proportions. It is a challenging task for an electronic nose to recognize the gas mixtures. Most current research is based on the overall response of sensors and uses relatively simple datasets, which cannot be used for complex mixtures or rapid monitoring scenarios. In this study, a novel electronic nose (E-nose) using a spiking neural network (SNN) model was proposed for the detection and recognition of gas mixtures. The electronic nose integrates six commercial metal oxide sensors for automated gas acquisition. SNN with a simple three-layer structure was introduced to extract transient dynamic information and estimate concentration rapidly. Then, a dataset of mixed gases with different orders of magnitude was established by the E-nose to verify the model’s performance. Additionally, random forests and the decision tree regression model were used for comparison with the SNN-based model. Results show that the model utilizes the dynamic characteristics of the sensors, achieving smaller mean squared error (MSE < 0.01) and mean absolute error (MAE) with less data compared to random forest and decision tree algorithms. In conclusion, the electronic nose system combined with the bionic model shows a high performance in identifying gas mixtures, which has a great potential to be used for indoor air quality monitoring in practical applications. Full article
(This article belongs to the Special Issue Gas Sensors and Electronic Noses for the Real Condition Sensing)
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20 pages, 4675 KiB  
Review
Organelle Targeting Self-Assembled Fluorescent Probe for Anticancer Treatment
by Md Sajid Hasan, Sangpil Kim, Chaelyeong Lim, Jaeeun Lee, Min-Seok Seu and Ja-Hyoung Ryu
Chemosensors 2024, 12(7), 138; https://doi.org/10.3390/chemosensors12070138 - 11 Jul 2024
Viewed by 1043
Abstract
Organic fluorescent probes have attracted attention for bioimaging due to their advantages, including high sensitivity, biocompatibility, and multi-functionality. However, some limitations related to low signal-to-background ratio and false positive and negative signals make them difficult for in situ target detection. Recently, organelle targeting [...] Read more.
Organic fluorescent probes have attracted attention for bioimaging due to their advantages, including high sensitivity, biocompatibility, and multi-functionality. However, some limitations related to low signal-to-background ratio and false positive and negative signals make them difficult for in situ target detection. Recently, organelle targeting self-assembled fluorescent probes have been studied to meet this demand. Most of the dye molecules suffer from a quenching effect, but, specifically, some dyes like Pyrene, Near-Infrared (NIR), Nitrobenzoxadiazole (NBD), Fluorescein isothiocyanate (FITC), Naphthalenediimides (NDI), and Aggregation induced emission (AIE) show unique characteristics when they undergo self-assembly or aggregation. Therefore, in this review, we classified the molecules according to the dye type and provided an overview of the organelle-targeting strategy with an emphasis on the construction of fluorescent nanostructures within complex cellular environments. Results demonstrated that fluorescent probes effectively target and localized inside the organelles (mitochondria, lysosome, and golgi body) and undergo self-assembly to form various nanostructures that possess bio-functionality with long retention time, organelles membrane disruption/ROS generation/enzyme activity suppression ability, and enhanced photodynamic properties for anticancer treatment. Furthermore, we systematically discussed the challenges that remain to be resolved for the high performance of these probes and mentioned some of the future directions for the design of molecules. Full article
(This article belongs to the Special Issue A Theme Issue in Honor of Dr. Richard Horobin—Cell or Organelle Selective Fluorescent Probes: Their Design, Mechanism, Modeling and Application)
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12 pages, 6533 KiB  
Article
SERS Substrate Based on Ag Nanoparticles@Layered Double Hydroxide@graphene Oxide and Au@Ag Core–Shell Nanoparticles for Detection of Two Taste and Odor Compounds
by Zhixiong Lao, Mingmin Zhong, Yin Liang, Jianrong Tan, Xiaoyan Liang, Wucheng Xie, Yong Liang and Jun Wang
Chemosensors 2024, 12(7), 137; https://doi.org/10.3390/chemosensors12070137 - 11 Jul 2024
Viewed by 556
Abstract
Sulfide organics and phenols are ubiquitous in freshwater lakes all over the world. As two taste and odor (T and O) compounds, they are harmful to the environment and human body. The existing detection methods for T and O compounds mainly include sensory [...] Read more.
Sulfide organics and phenols are ubiquitous in freshwater lakes all over the world. As two taste and odor (T and O) compounds, they are harmful to the environment and human body. The existing detection methods for T and O compounds mainly include sensory analysis and gas-phase mass spectrometry, which are cumbersome and time-consuming. Herein, a method for the simultaneous and rapid detection of two T and O compounds (methyl sulfide and 2,4-di-tert-butylphenol) based on surface-enhanced Raman spectroscopy (SERS) is firstly developed. The SERS substrate was prepared by coating Ag nanoparticles (Ag NPs), layered double hydroxide (LDH), and graphene oxide (GO) on the surface of an Ag-coated Au nanoparticle (Au@Ag NP) substrate. Under optimal conditions, this SERS substrate possessed low detection limits of 1.53 ppm for methyl sulfide and 0.39 ppm for 2,4-di-tert-butylphenol. In addition, it took only 20 min to complete the detection using this method, without complex sample pretreatment. Furthermore, it was successfully applied to simultaneously detect methyl sulfide and 2,4-di-tert-butylphenol in actual water samples and had good application prospects for the rapid detection of T and O compounds in water. Full article
(This article belongs to the Special Issue Nanomaterials in Chemosensors and Biosensors: Development and Application)
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13 pages, 2839 KiB  
Article
Molecular Understanding of the Surface-Enhanced Raman Spectroscopy Salivary Fingerprint in People after Sars-COV-2 Infection and in Vaccinated Subjects
by Francesca Rodà, Alice Gualerzi, Silvia Picciolini, Luana Forleo, Valentina Mangolini, Roberta Mancuso, Simone Agostini, Rudy Alexander Rossetto, Paola Pierucci, Paolo Innocente Banfi and Marzia Bedoni
Chemosensors 2024, 12(7), 136; https://doi.org/10.3390/chemosensors12070136 - 11 Jul 2024
Viewed by 741
Abstract
The rapid spread of SARS-COV-2 and the millions of worldwide deaths and hospitalizations have prompted an urgent need for the development of screening tests capable of rapidly and accurately detecting the virus, even in asymptomatic people. The easy collection and the biomarker content [...] Read more.
The rapid spread of SARS-COV-2 and the millions of worldwide deaths and hospitalizations have prompted an urgent need for the development of screening tests capable of rapidly and accurately detecting the virus, even in asymptomatic people. The easy collection and the biomarker content of saliva, together with the label-free and informative power of surface-enhanced Raman spectroscopy (SERS) analysis have driven the creation of point-of-care platforms capable of identifying people with COVID-19. Indeed, different salivary fingerprints were observed between uninfected and infected people. Hence, we performed a retrospective analysis of SERS spectra from salivary samples of COVID-19-infected and -vaccinated subjects to understand if viral components and/or the immune response are implicated in spectral variations. The high sensitivity of the proposed SERS-based method highlighted the persistence of molecular alterations in saliva up to one month after the first positive swab, even when the subject tested negative for the rapid antigenic test. Nevertheless, no specific spectral patterns attributable to some viral proteins and immunoglobulins involved in COVID-19 infection and its progression were found, even if differences in peak intensity, presence, and position were observed in the salivary SERS fingerprint. Full article
(This article belongs to the Special Issue Raman and Surface-Enhanced Raman Scattering Techniques in Analytical and Biomedical Fields)
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31 pages, 9994 KiB  
Review
Recent Advances in the Application of Metal–Organic Frameworks and Coordination Polymers in Electrochemical Biosensors
by Alemayehu Kidanemariam and Sungbo Cho
Chemosensors 2024, 12(7), 135; https://doi.org/10.3390/chemosensors12070135 - 9 Jul 2024
Viewed by 1041
Abstract
Electrochemical biosensors are critical in advancing biomedical and pharmaceutical therapies because of their adaptability and cost-effectiveness. Voltammetric and amperometric sensors are of particular interest. These sensors typically consist of a specialized tip or biorecognition element and a transducer that converts biological data into [...] Read more.
Electrochemical biosensors are critical in advancing biomedical and pharmaceutical therapies because of their adaptability and cost-effectiveness. Voltammetric and amperometric sensors are of particular interest. These sensors typically consist of a specialized tip or biorecognition element and a transducer that converts biological data into readable signals. Efficient biosensor materials are essential for addressing health emergencies, with coordination polymers (CPs) and metal–organic frameworks (MOFs) showing promise. Functionalization strategies are necessary to enhance the usability of pristine MOFs, owing to issues such as low conductivity. The integration of conductive polymers with MOFs has resulted in the development of highly efficient biosensors. Both enzymatic and nonenzymatic biosensors are used for analyte detection; nonenzymatic approaches are gaining popularity owing to their durability and accuracy. MOFs and CPs have been applied in sensitive electrochemical biosensors to detect fatal brain tumors such as glioblastomas (GBM). These biosensors demonstrate enhanced selectivity and sensitivity, highlighting the potential of MOFs and CPs in advancing electrochemical biosensor technology for both in vivo and in vitro applications. Full article
(This article belongs to the Special Issue Electrochemical Sensing in Medical Diagnosis)
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13 pages, 2616 KiB  
Article
Enhancement of Ion-Sensitive Field-Effect Transistors through Sol-Gel Processed Lead Zirconate Titanate Ferroelectric Film Integration and Coplanar Gate Sensing Paradigm
by Dong-Gyun Mah, Seong-Moo Oh, Jongwan Jung and Won-Ju Cho
Chemosensors 2024, 12(7), 134; https://doi.org/10.3390/chemosensors12070134 - 9 Jul 2024
Viewed by 726
Abstract
To facilitate the utility of field effect transistor (FET)-type sensors, achieving sensitivity enhancement beyond the Nernst limit is crucial. Thus, this study proposed a novel approach for the development of ferroelectric FETs (FeFETs) using lead zirconate titanate (PZT) ferroelectric films integrated with indium–tungsten [...] Read more.
To facilitate the utility of field effect transistor (FET)-type sensors, achieving sensitivity enhancement beyond the Nernst limit is crucial. Thus, this study proposed a novel approach for the development of ferroelectric FETs (FeFETs) using lead zirconate titanate (PZT) ferroelectric films integrated with indium–tungsten oxide (IWO) channels synthesized via a cost-effective sol-gel process. The electrical properties of PZT-IWO FeFET devices were significantly enhanced through the strategic implementation of PZT film treatment by employing intentional annealing procedures. Consequently, key performance metrics, including the transfer curve on/off ratio and subthreshold swings, were improved. Moreover, unprecedented electrical stability was realized by eliminating the hysteresis effect during double sweeps. By leveraging a single-gate configuration as an FeFET transformation element, extended-gate (EG) detection methodologies for pH sensing were explored, thereby introducing a pioneering dimension to sensor architecture. A measurement paradigm inspired by plane gate work was adopted, and the proposed device exhibited significant resistive coupling, consequently surpassing the sensitivity thresholds of conventional ion-sensitive field-effect transistors. This achievement represents a substantial paradigm shift in the landscape of ion-sensing methodologies, surpassing the established Nernst limit (59.14 mV/pH). Furthermore, this study advances FeFET technology and paves the way for the realization of highly sensitive and reliable ion sensing modalities. Full article
(This article belongs to the Collection pH Sensors, Biosensors and Systems)
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8 pages, 769 KiB  
Brief Report
Validation of a Headspace Gas Chromatography with Flame Ionization Detection Method to Quantify Blood Alcohol Concentration (BAC) for Forensic Practice
by Alice Cerioni, Gianmario Mietti, Marta Cippitelli, Giulia Ricchezze, Erika Buratti, Rino Froldi, Mariano Cingolani and Roberto Scendoni
Chemosensors 2024, 12(7), 133; https://doi.org/10.3390/chemosensors12070133 - 9 Jul 2024
Viewed by 739
Abstract
Alcohol consumption is a major social and forensic issue. It is often the cause of road accidents, industrial accidents, suicides and other crimes. On account of this, it is of fundamental importance in forensic toxicology to correctly quantify blood alcohol concentration (BAC). In [...] Read more.
Alcohol consumption is a major social and forensic issue. It is often the cause of road accidents, industrial accidents, suicides and other crimes. On account of this, it is of fundamental importance in forensic toxicology to correctly quantify blood alcohol concentration (BAC). In this work, a straightforward method for the quantification of ethanol from blood samples by means of headspace gas chromatography with flame ionization detection is presented and validated. For method validation linearity, limit of detection (LOD), lower limit of quantification (LLOQ), accuracy, precision (% CV) and interference studies were carried out. All the validation conditions were satisfied according to the acceptance criteria. Proof of applicability was performed on 50 real blood samples, showing that the method was effective. Full article
(This article belongs to the Special Issue GC, MS and GC-MS Analytical Methods: Opportunities and Challenges (Second Edition))
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13 pages, 2317 KiB  
Article
A Rapid and Interference-Resistant Formaldehyde Detection Method Based on Surface-Enhanced Raman Spectroscopy with a Reaction-Induced Self-Amplification Strategy
by Chen Wang, Yanli Gao, Xinrong Qiu, Lifang Nie, Yang Liu, Rigui Zhou, Hongpeng Wang and Shengjun Xiong
Chemosensors 2024, 12(7), 132; https://doi.org/10.3390/chemosensors12070132 - 8 Jul 2024
Viewed by 656
Abstract
Formaldehyde is widely utilized across various industries such as food, textiles, and leather, yet its presence raises significant health concerns due to its irritation and carcinogenicity. Numerous methods have been developed to probe it in solution and gas states. Among them, absorption spectroscopy-based [...] Read more.
Formaldehyde is widely utilized across various industries such as food, textiles, and leather, yet its presence raises significant health concerns due to its irritation and carcinogenicity. Numerous methods have been developed to probe it in solution and gas states. Among them, absorption spectroscopy-based methods commonly employed. However, these methods require complex preprocessing for colored solutions to avoid interference. In response to this challenge, a novel interference-resistant detection kit leveraging surface-enhanced Raman spectroscopy (SERS) coupled with reaction-induced self-amplification for rapid and direct detection of formaldehyde was developed. The kit needed only ten minutes and achieved a limit of detection lower than 10−4 μg/mL with a handheld Raman spectrometer. Thanks to the kit’s reaction with formaldehyde, colloidal nanoparticles were linked to form “hot-spots” to further enhance the SERS signals. The signal demonstrated outstanding resistance to interference, including different dyes, ensuring a practical tool for direct detection of formaldehyde in complex solutions. Full article
(This article belongs to the Special Issue Advanced Spectroscopy Technology for Chemical Qualitative and Quantitative Analysis)
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23 pages, 2802 KiB  
Article
Unveiling Hidden Insights in Gas Chromatography Data Analysis with Generative Adversarial Networks
by Namkyung Yoon, Wooyong Jung and Hwangnam Kim
Chemosensors 2024, 12(7), 131; https://doi.org/10.3390/chemosensors12070131 - 7 Jul 2024
Viewed by 728
Abstract
The gas chromatography analysis method for chemical substances enables accurate analysis to precisely distinguish the components of a mixture. This paper presents a technique for augmenting time-series data of chemicals measured by gas chromatography instruments with artificial intelligence techniques such as generative adversarial [...] Read more.
The gas chromatography analysis method for chemical substances enables accurate analysis to precisely distinguish the components of a mixture. This paper presents a technique for augmenting time-series data of chemicals measured by gas chromatography instruments with artificial intelligence techniques such as generative adversarial networks (GAN). We propose a novel GAN algorithm called GCGAN for gas chromatography data, a unified model of autoencoder (AE) and GAN for effective time-series data learning with an attention mechanism. The proposed GCGAN utilizes AE to learn a limited number of data more effectively. We also build a layer of high-performance generative adversarial neural networks based on the analysis of the features of data measured by gas chromatography instruments. Then, based on the proposed learning, we synthesize the features embedded in the gas chromatography data into a feature distribution that extracts the temporal variability. GCGAN synthesizes the features embedded in the gas chromatography data into a feature distribution that extracts the temporal variability of the data over time. We have fully implemented the proposed GCGAN and experimentally verified that the data augmented by the GCGAN have the characteristic properties of the original gas chromatography data. The augmented data demonstrate high quality with the Pearson correlation coefficient, Spearman correlation coefficient, and cosine similarity all exceeding 0.9, significantly enhancing the performance of AI classification models by 40%. This research can be effectively applied to various small dataset domains other than gas chromatography data, where data samples are limited and difficult to obtain. Full article
(This article belongs to the Collection Recent Advances in Multifunctional Sensing Technology for Gas Analysis)
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23 pages, 7107 KiB  
Article
Profiling of Organosulfur Compounds in Onions: A Comparative Study between LC-HRMS and DTD-GC-MS
by Ana V. González-de-Peredo, Alicia Maroto, Gerardo F. Barbero and Antony Memboeuf
Chemosensors 2024, 12(7), 130; https://doi.org/10.3390/chemosensors12070130 - 6 Jul 2024
Viewed by 720
Abstract
Onions are known not only for their culinary importance but also for their nutritional and health-promoting properties. Both properties are closely linked to their content of organosulfur compounds, which account for up to 5% of the dry weight of an onion. Given the [...] Read more.
Onions are known not only for their culinary importance but also for their nutritional and health-promoting properties. Both properties are closely linked to their content of organosulfur compounds, which account for up to 5% of the dry weight of an onion. Given the importance of these compounds, suitable analytical methods are required for their study. Two techniques should be highlighted in this context: gas chromatography coupled to mass spectrometry (GC-MS), and liquid chromatography coupled to mass spectrometry (LC-MS). In this study, eight different onion varieties were analyzed using two distinct analytical techniques: direct thermal desorption–gas chromatography–mass spectrometry (DTD-GC-MS) and high-resolution mass spectrometry (HRMS) on an LC-ESI-QqTOF instrument. Each method identified different organosulfur compounds, with LC-HRMS targeting 15 non-volatile compounds, such as cysteine sulfoxides, and GC-MS targeting 18 volatiles, such as disulfides and trisulfides. The results obtained were studied using Pearson correlations and principal component analysis. No precise correlation was found between the initial organosulfur compounds in onions and their hydrolysates. Consequently, although GC is one of the most employed techniques in the scientific literature, the use of LC-HRMS or a combination of both techniques may offer a more comprehensive and accurate description of the metabolomic profile of onions. Full article
(This article belongs to the Special Issue Advanced Spectroscopy Technology for Chemical Qualitative and Quantitative Analysis)
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25 pages, 6056 KiB  
Review
Recent Development of Electrospun Nanostructured Fibers as Colorimetric Probes for Metal Ion Sensing: A Review
by Mohanraj Jagannathan, Ravi Kumar Yohan and Sungbo Cho
Chemosensors 2024, 12(7), 129; https://doi.org/10.3390/chemosensors12070129 - 5 Jul 2024
Viewed by 787
Abstract
The colorimetric detection of metal ions has witnessed a surge in advancements, with nanostructured fibers emerging as a powerful platform for environmental monitoring and remediation applications. These fibers offer several advantages, including a high surface area, enhanced sensitivity and selectivity, non-intrusive analysis, rapid [...] Read more.
The colorimetric detection of metal ions has witnessed a surge in advancements, with nanostructured fibers emerging as a powerful platform for environmental monitoring and remediation applications. These fibers offer several advantages, including a high surface area, enhanced sensitivity and selectivity, non-intrusive analysis, rapid response times, robustness under harsh conditions, and user-friendly handling. This unique combination makes them particularly suitable for visible eye detection of metal ions in remote or challenging environments. This review provides a concise overview of recent developments in nanostructured fibers, and their cutting-edge fabrication methods, for the colorimetric-based detection of various heavy metal ions in real-time samples. By exploiting the unique properties of these fibers, colorimetric detection offers a promising and cost-effective approach for heavy metal ion determination. This review delves into the design principles, functionalization strategies, and detection mechanisms employed in these innovative sensors. We highlight the potential of nanostructured fibers as a well-established and efficient platform for the colorimetric detection of heavy metals, paving the way for more sustainable and accessible environmental monitoring solutions. Full article
(This article belongs to the Special Issue Colorimetric and Fluorescent Sensors: Current Status and Future Development)
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14 pages, 6473 KiB  
Article
Research on the Detection of Hg(II) in Seawater Using GR-MWCNTs/CeO2-Modified Electrodes
by Huili Hao, Chengjun Qiu, Wei Qu, Yuan Zhuang, Xiaochun Han, Wei Tao, Yang Gu, Zizi Zhao, Haozheng Liu and Wenhao Wang
Chemosensors 2024, 12(7), 128; https://doi.org/10.3390/chemosensors12070128 - 4 Jul 2024
Viewed by 635
Abstract
Hg(II), as an extremely hazardous heavy metal contaminant in the environment, poses a significant potential hazard to human health and ecosystems. A GR-MWCNTs-COOH/CeO2/Nafion composite film-modified glassy carbon electrode was prepared using the drop-casting method in this study. The GR-MWCNTs-COOH/CeO2/Nafion/GCE [...] Read more.
Hg(II), as an extremely hazardous heavy metal contaminant in the environment, poses a significant potential hazard to human health and ecosystems. A GR-MWCNTs-COOH/CeO2/Nafion composite film-modified glassy carbon electrode was prepared using the drop-casting method in this study. The GR-MWCNTs-COOH/CeO2/Nafion/GCE was electrochemically investigated through cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). Additionally, the surface morphologies of the composite film were evaluated using scanning electron microscopy (SEM). The conditions, such as buffer solution, pH, deposition potential, deposition time, modified film thickness, and Nafion content, were optimized. Under optimal experimental conditions, a good linear relationship between the peak current response of Hg(II) and its concentration in the range of 5–100 μg·L−1 was observed, with a detection limit of 0.389 μg·L−1. When it was used to detect Hg(II) in offshore seawater, the recovery rate ranged from 94.72% to 103.8%, with RSDs ≤ 5.79%. Full article
(This article belongs to the Special Issue Preparation and Application of Photoelectrochemical Sensors)
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16 pages, 5647 KiB  
Article
Response Time Dynamics of a Membrane-Based Microfluidic Gas Sensor
by Sreerag Kaaliveetil, Najamuddin Naveed Khaja, Niranjan Haridas Menon and Sagnik Basuray
Chemosensors 2024, 12(7), 127; https://doi.org/10.3390/chemosensors12070127 - 3 Jul 2024
Viewed by 3433
Abstract
Practical gas–liquid interfacing is paramount in microfluidic technology, particularly in developing microfluidic gas sensors. We have created an easily replicable membrane-based closed microfluidic platform (MB-MP) to achieve in situ gas–liquid contact for low-resource settings. We have fabricated the MB-MP using readily available materials [...] Read more.
Practical gas–liquid interfacing is paramount in microfluidic technology, particularly in developing microfluidic gas sensors. We have created an easily replicable membrane-based closed microfluidic platform (MB-MP) to achieve in situ gas–liquid contact for low-resource settings. We have fabricated the MB-MP using readily available materials like double-sided tape or parafilm without conventional soft lithographic techniques. The response characteristics of the MB-MP are studied using CO2 as the model gas and bromothymol blue dye as the sensing material. The dye’s color change, indicative of pH shifts due to CO2 absorption, is captured with a digital microscope and analyzed via the ImageJ software package v1.54g. The response shows saturation and regeneration parts when cycled between CO2 and N2, respectively. Experiments are conducted to investigate the response characteristics and saturation rate under different conditions, including changes in volumetric flow rate, gas stream velocity, and dye solution volume. We observe experimentally that an increase in volumetric flow rate decreases the delay and increases the saturation rate of the response, surpassing the impact of the gas stream’s increased velocity. Furthermore, increasing the dye volume results in an exponential decrease in the saturation rate and an increase in the delay. These insights are essential for optimizing the platform’s response for point-of-use applications. Full article
(This article belongs to the Special Issue Chemical Sensors Based on Low-Dimensional Semiconductors)
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16 pages, 5170 KiB  
Article
Development of Electrochemical and Colorimetric Biosensors for Detection of Dopamine
by Rimsha Khan, Saima Anjum, Nishat Fatima, Nosheen Farooq, Aqeela Shaheen, Javier Fernandez Garcia, Muhammad Imran Khan and Abdallah Shanableh
Chemosensors 2024, 12(7), 126; https://doi.org/10.3390/chemosensors12070126 - 3 Jul 2024
Viewed by 902
Abstract
Neurotransmitters are essential chemical messengers required for proper brain function, and any changes in their concentrations can lead to neuronal diseases. Therefore, sensitive and selective detection is crucial. This study presents a fast and simple colorimetric method for dopamine detection using three reagent [...] Read more.
Neurotransmitters are essential chemical messengers required for proper brain function, and any changes in their concentrations can lead to neuronal diseases. Therefore, sensitive and selective detection is crucial. This study presents a fast and simple colorimetric method for dopamine detection using three reagent solutions: AgNP and MPA, Ag/Au nanocomposite, and mercaptophenylacetic acid. TEM images showed a narrow distribution of Ag and Au nanoparticles with average sizes of 20 nm and 13 nm, respectively, with gold nanoparticles bound to the edges of silver nanoparticles. A paper-based biosensor was created using manual wax printing for the colorimetric detection of dopamine. Visual detection onsite showed color changes with both the silver nanoparticles and mercaptophenylacetic acid mixture and the silver–gold nanoparticle composite. Electrochemical detection using a glassy carbon electrode modified with 8 mM mercaptophenylacetic acid demonstrated high selectivity and sensitivity towards dopamine, with a peak in the range of 0.7–0.9 V. Interferences were minimized, ensuring high sensitivity and selective detection of dopamine. Full article
(This article belongs to the Section (Bio)chemical Sensing)
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15 pages, 4134 KiB  
Article
Research on the Evaluation of Baijiu Flavor Quality Based on Intelligent Sensory Technology Combined with Machine Learning
by Aliya, Shi Liu, Danni Zhang, Yufa Cao, Jinyuan Sun, Shui Jiang and Yuan Liu
Chemosensors 2024, 12(7), 125; https://doi.org/10.3390/chemosensors12070125 - 3 Jul 2024
Viewed by 814
Abstract
Baijiu, one of the world’s six major distilled spirits, has an extremely rich flavor profile, which increases the complexity of its flavor quality evaluation. This study employed an electronic nose (E-nose) and electronic tongue (E-tongue) to detect 42 types of strong-aroma Baijiu. Linear [...] Read more.
Baijiu, one of the world’s six major distilled spirits, has an extremely rich flavor profile, which increases the complexity of its flavor quality evaluation. This study employed an electronic nose (E-nose) and electronic tongue (E-tongue) to detect 42 types of strong-aroma Baijiu. Linear discriminant analysis (LDA) was performed based on the different production origins, alcohol content, and grades. Twelve trained Baijiu evaluators participated in the quantitative descriptive analysis (QDA) of the Baijiu samples. By integrating characteristic values from the intelligent sensory detection data and combining them with the human sensory evaluation results, machine learning was used to establish a multi-submodel-based flavor quality prediction model and classification model for Baijiu. The results showed that different Baijiu samples could be well distinguished, with a prediction model R2 of 0.9994 and classification model accuracy of 100%. This study provides support for the establishment of a flavor quality evaluation system for Baijiu. Full article
(This article belongs to the Special Issue Electrochemical Sensor Array for Food Detection and Human Perception)
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15 pages, 3546 KiB  
Article
Urea Biosensing through Integration of Urease to the PEDOT-Polyamine Conducting Channels of Organic Electrochemical Transistors: pH-Change-Based Mechanism and Urine Sensing
by Jael R. Neyra Recky, Marjorie Montero-Jimenez, Juliana Scotto, Omar Azzaroni and Waldemar A. Marmisollé
Chemosensors 2024, 12(7), 124; https://doi.org/10.3390/chemosensors12070124 - 3 Jul 2024
Viewed by 893
Abstract
We present the construction of an organic electrochemical transistor (OECT) based on poly(3,4-ethylendioxythiophene, PEDOT) and polyallylamine (PAH) and its evaluation as a bioelectronic platform for urease integration and urea sensing. The OECT channel was fabricated in a one-step procedure using chemical polymerization. Then, [...] Read more.
We present the construction of an organic electrochemical transistor (OECT) based on poly(3,4-ethylendioxythiophene, PEDOT) and polyallylamine (PAH) and its evaluation as a bioelectronic platform for urease integration and urea sensing. The OECT channel was fabricated in a one-step procedure using chemical polymerization. Then, urease was immobilized on the surface by electrostatic interaction of the negatively charged enzyme at neutral pH with the positively charged surface of PEDOH-PAH channels. The real-time monitoring of the urease adsorption process was achieved by registering the changes on the drain–source current of the OECT upon continuous scan of the gate potential during enzyme deposition with high sensitivity. On the other hand, integrating urease enabled urea sensing through the transistor response changes resulting from local pH variation as a consequence of enzymatic catalysis. The response of direct enzyme adsorption is compared with layer-by-layer integration using polyethylenimine. Integrating a polyelectrolyte over the adsorbed enzyme resulted in a more stable response, allowing for the sensing of urine even from diluted urine samples. These results demonstrate the potential of integrating enzymes into the active channels of OECTs for the development of biosensors based on local pH changes. Full article
(This article belongs to the Special Issue Electrochemical Biosensors: Advances and Prospects)
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14 pages, 1793 KiB  
Article
Environmental Pollution Monitoring via Capillary Zone Electrophoresis and UHPLC Simultaneous Quantification of Some Antipsychotic Drug Residues in Industrial Wastewater Effluents
by Alhumaidi B. Alabbas, Rachid Slimani, Imane El Ouahabi, Abdelkader Zarrouk, Said Lazar, Rachid Azzallou, Noha F. Shalaby and Sherif A. Abdel-Gawad
Chemosensors 2024, 12(7), 123; https://doi.org/10.3390/chemosensors12070123 - 2 Jul 2024
Viewed by 592
Abstract
Monitoring and measuring pharmaceutical pollutants in environmental samples is a vital and complex task due to their potential detrimental effects on human health, even at low levels. Using capillary zone electrophoresis (CZE) and ultra-high-performance liquid chromatography (UHPLC), it was possible to separate and [...] Read more.
Monitoring and measuring pharmaceutical pollutants in environmental samples is a vital and complex task due to their potential detrimental effects on human health, even at low levels. Using capillary zone electrophoresis (CZE) and ultra-high-performance liquid chromatography (UHPLC), it was possible to separate and measure three commonly used antipsychotic drugs, chlorpromazine (CPZ), haloperidol (HAL), and risperidone (RIS), in wastewater of the pharmaceutical industry. The technique of solid-phase extraction (SPE) was developed and implemented as a very effective method for preparing samples prior to analysis. The settings of the capillary electrophoretic and chromatographic techniques were adjusted to obtain the most efficient separation profile for the medications being studied. The concentration of all the medicines being investigated ranged from 0.5 to 50 µg/mL. SPE was used to treat real wastewater samples after a thorough validation process that followed the rules set by ICH-Q2B. The developed assays were then effectively employed to identify the tested antipsychotic substances in the real wastewater samples. The provided methodologies may be efficiently utilized to monitor the extent of environmental contamination caused by the investigated pharmaceuticals. Full article
(This article belongs to the Special Issue Chemical Sensors and Analytical Methods for Environmental Monitoring)
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17 pages, 2830 KiB  
Article
Electrochemical Detection of Acetaminophen in Pharmaceuticals Using Rod-Shaped α-Bi2O3 Prepared via Reverse Co-Precipitation
by Ljubica Andjelković, Slađana Đurđić, Dalibor Stanković, Aleksandar Kremenović, Vladimir B. Pavlović, Dejan A. Jeremić and Marija Šuljagić
Chemosensors 2024, 12(7), 122; https://doi.org/10.3390/chemosensors12070122 - 2 Jul 2024
Viewed by 604
Abstract
This study employed a novel synthetic approach involving a modified reverse co-precipitation method utilizing glacial acetic acid to synthesize α-Bi2O3. X-ray powder diffraction and scanning and transmission electron microscopy analyses revealed the formation of a rod-like α-Bi2O [...] Read more.
This study employed a novel synthetic approach involving a modified reverse co-precipitation method utilizing glacial acetic acid to synthesize α-Bi2O3. X-ray powder diffraction and scanning and transmission electron microscopy analyses revealed the formation of a rod-like α-Bi2O3 microstructure. The prepared material was utilized to modify a glassy carbon paste (GCP) electrode for the development of an electrochemical sensor for acetaminophen (APAP) detection using differential pulse voltammetry (DPV). Cyclic voltammetry studies revealed that the GCP@Bi2O3 electrode exhibited enhanced electrochemical properties compared to the bare GCP. The designed GCP@Bi2O3 sensor detected APAP in the linear concentration range from 0.05 to 12.00 µM, with LOQ and LOD of 36 nM and 10 nM, respectively. Additionally, the developed sensor demonstrated sufficient precision, repeatability, and selectivity toward APAP detection. The recovery values between the declared and found APAP content in a pharmaceutical formulation (Caffetin®) displayed the advantageous accuracy, precision, and applicability of the GCP@Bi2O3 sensor and the developed DPV method for real-time APAP detection in pharmaceuticals, with minimal interference from the matrix effect. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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17 pages, 8490 KiB  
Article
Selective Determination of 4,4′-Oxydianiline (4,4′-ODA) in Plastic Packaging Using Molecularly Imprinted Polymer Sensor Integrated with Pyrolyzed Copper/Carbon Composite
by Xuejun Zhou, Pengcheng Ye, Zhiding Huang, Chun Yang, Jiefang Ren, Jin Wang and Shali Tang
Chemosensors 2024, 12(7), 121; https://doi.org/10.3390/chemosensors12070121 - 1 Jul 2024
Viewed by 808
Abstract
This study focuses on the synthesis, fabrication, and characterization of a molecularly imprinted polymer (MIP) sensor tailored for the selective determination of 4,4′-oxydianiline (4,4′-ODA) in plastic products. Notably, by integrating the sensor matrix with pyrolyzed copper/carbon material derived from Cu-BTC MOF, a remarkable [...] Read more.
This study focuses on the synthesis, fabrication, and characterization of a molecularly imprinted polymer (MIP) sensor tailored for the selective determination of 4,4′-oxydianiline (4,4′-ODA) in plastic products. Notably, by integrating the sensor matrix with pyrolyzed copper/carbon material derived from Cu-BTC MOF, a remarkable enhancement in electrochemical performance is achieved. The Cu-BTC material is grown successfully on the surface of carbon nanotubes (CNTs) and subjected to calcination at 800 °C, yielding a CNT/Cu/C composite. This composite exhibits an increased surface area and enhanced electron transfer capability, resulting in an improved current response. To augment the selective detection capability of the modified electrodes for 4,4′-ODA, molecularly imprinted polymers (MIPs) were incorporated onto the composite surface. The modified electrode (CNT-2/Cu/C/MIP/GCE) was synthesized using acrylamide (AM) and methacrylic acid (MAA) as dual-functional monomers with 4,4′-ODA as a template molecule via precipitation polymerization. The differential pulse voltammetric (DPV) current response to 4,4′-ODA showed a favorable linear relationship within the concentration range of (0.15–10 μM,10–100 μM), with a detection limit of 0.05 μM. Moreover, the CNT-2/Cu/C/MIP/GCE sensor demonstrates exceptional sensitivity, specificity, consistency, and durability. Furthermore, this approach has proven effective in detecting 4,4′-ODA in spiked nylon spatula samples, with recovery rates ranging from 86.3% to 103.5%. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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15 pages, 2372 KiB  
Article
Study on the Characterization and Degradation Pattern of Circular RNA Vaccines Using an HPLC Method
by Feiran Cheng, Ji Li, Chaoying Hu, Yu Bai, Jianyang Liu, Dong Liu, Qian He, Qiuheng Jin, Qunying Mao, Zhenglun Liang and Miao Xu
Chemosensors 2024, 12(7), 120; https://doi.org/10.3390/chemosensors12070120 - 1 Jul 2024
Viewed by 1210
Abstract
Circular RNA (circRNA) vaccines have attracted increasing attention due to their stable closed-loop structures and persistent protein expression ability. During the synthesis process, nicked circRNAs with similar molecular weights to those of circRNAs are generated. Analytical techniques based on differences in molecular weight, [...] Read more.
Circular RNA (circRNA) vaccines have attracted increasing attention due to their stable closed-loop structures and persistent protein expression ability. During the synthesis process, nicked circRNAs with similar molecular weights to those of circRNAs are generated. Analytical techniques based on differences in molecular weight, such as capillary electrophoresis, struggle to distinguish between circRNAs and nicked circRNAs. The characteristic degradation products of circRNAs and their biological activities remain unclear. Therefore, developing methods to identify target circRNAs and non-target components and investigating degradation patterns will be beneficial to gaining an in-depth understanding of the properties and quality control of circRNAs vaccines. The reversed-phase HPLC (RP-HPLC) method was established for identification of target circRNAs, product-related substances, and impurities. Subsequently, we investigated the degradation patterns of circRNAs under thermal acceleration conditions and performed biological analysis of degradation products and linear precursors. Here, RP-HPLC method effectively identified circRNAs and nicked circRNAs. With thermal acceleration, circRNAs exhibited a “circular→nicked circRNAs→degradation products” degradation pattern. Biological analysis revealed that the immunogenicity of degradation products significantly decreased, whereas linear precursors did not possess immunogenicity. Thus, our established RP-HPLC method can be used for purity analysis of circRNA vaccines, which contributes to the quality control of circRNA vaccines and promoting the development of circRNA technology. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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15 pages, 1876 KiB  
Article
Microflow Injection System for Efficient Cu(II) Detection across a Broad Range
by David Ricart, Antonio David Dorado, Conxita Lao-Luque and Mireia Baeza
Chemosensors 2024, 12(7), 119; https://doi.org/10.3390/chemosensors12070119 - 29 Jun 2024
Viewed by 603
Abstract
In this study, a modular, multi-step, photometric microflow injection analysis (micro-FIA) system for the automatic determination of Cu(II) in a bioreactor was developed. The system incorporates diverse 3D-printed modules, including a platform formed by a mixer module to mix Cu(II) with hydroxylamine, which [...] Read more.
In this study, a modular, multi-step, photometric microflow injection analysis (micro-FIA) system for the automatic determination of Cu(II) in a bioreactor was developed. The system incorporates diverse 3D-printed modules, including a platform formed by a mixer module to mix Cu(II) with hydroxylamine, which reduces Cu(II) to Cu(I) linked to a diluter module via a Tesla valve, a chelation mixer module, a disperser module, and a detector module provided by an LED light source at λ = 455 nm and a light dependence resistor (LDR) as a light intensity detector. The system measures the color intensity resulting from the chelation between Cu(I) and neocuproine. The micro-FIA system demonstrated good capability for automatic and continuous Cu(II) determination, in a wide range of Cu concentrations, from 34 to 2000 mg L−1. The device exhibits a good repeatability (coefficient of variation below 2% across the measured concentration range), good reproducibility, and has an accuracy of around 100% between 600 and 1900 mg L−1. Real samples were analyzed using both the micro-FIA system and an atomic absorption spectroscopy method, revealing no statistically significant differences. Additionally, a Tesla valve located before the detector substituted a 3-way solenoid valve, eliminating the need for moving parts. Full article
(This article belongs to the Special Issue Microfluidic Device Based Chemical and Biochemical Sensors)
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14 pages, 4702 KiB  
Article
Shungite Paste Electrodes: Basic Characterization and Initial Examples of Applicability in Electroanalysis
by Michaela Bártová, Martin Bartoš, Ivan Švancara and Milan Sýs
Chemosensors 2024, 12(7), 118; https://doi.org/10.3390/chemosensors12070118 - 28 Jun 2024
Viewed by 490
Abstract
This article introduces a new type of carbon paste electrode prepared from black raw shungite. In powdered form, this carbonaceous material was mixed with several nonpolar binders. The resulting shungite pastes were microscopically and electrochemically characterized. Mixtures of several pasting liquids with different [...] Read more.
This article introduces a new type of carbon paste electrode prepared from black raw shungite. In powdered form, this carbonaceous material was mixed with several nonpolar binders. The resulting shungite pastes were microscopically and electrochemically characterized. Mixtures of several pasting liquids with different contents of shungite powder were tested to select the optimal composition and compared with other types of carbon paste-based electrodes made of graphite and glassy carbon powder. In terms of physical and mechanical properties, shungite paste electrodes (ShPEs) formed a composite mass being like dense pastes from glassy carbon microspheres, having harder consistency than that of traditional graphitic carbon pastes. The respective electrochemical measurements with ShPEs were based on cyclic voltammetry of ferri-/ferro-cyanide redox pairs, allowing us to evaluate some typical parameters such as electrochemically active surface area, double-layer capacitance, potential range in the working media given, heterogeneous rate constant, charge-transfer coefficient, exchange current density, and open-circuit potential. The whole study with ShPEs was then completed with three different examples of possible electroanalytical applications, confirming that the carbon paste-like configuration with powdered shungite represents an environmentally friendly (green) and low-cost electrode material with good stability in mixed aqueous-organic mixtures, and hence with interesting prospects in electroanalysis of biologically active organic compounds. It seems that similar analytical parameters of the already established variants of carbon paste electrodes can also be expected for their shungite analogues. Full article
(This article belongs to the Special Issue Recent Advances in Electrode Materials for Electrochemical Sensing)
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17 pages, 4876 KiB  
Article
Electronic Nose and GC-MS Analysis to Detect Mango Twig Tip Dieback in Mango (Mangifera indica) and Panama Disease (TR4) in Banana (Musa acuminata)
by Wathsala Ratnayake, Stanley E. Bellgard, Hao Wang and Vinuthaa Murthy
Chemosensors 2024, 12(7), 117; https://doi.org/10.3390/chemosensors12070117 - 24 Jun 2024
Viewed by 806
Abstract
Volatile organic compounds (VOCs), as a biological element released from plants, have been correlated with disease status. Although analysis of VOCs using GC-MS is a routine procedure, it has limitations, including being time-consuming, laboratory-based, and requiring specialist training. Electronic nose devices (E-nose) provide [...] Read more.
Volatile organic compounds (VOCs), as a biological element released from plants, have been correlated with disease status. Although analysis of VOCs using GC-MS is a routine procedure, it has limitations, including being time-consuming, laboratory-based, and requiring specialist training. Electronic nose devices (E-nose) provide a portable and rapid alternative. This is the first pilot study exploring three types of commercially available E-nose to assess how accurately they could detect mango twig tip dieback and Panama disease in bananas. The devices were initially trained and validated on known volatiles, then pure cultures of Pantoea sp., Staphylococcus sp., and Fusarium odoratissimum, and finally, on infected and healthy mango leaves and field-collected, infected banana pseudo-stems. The experiments were repeated three times with six replicates for each host-pathogen pair. The variation between healthy and infected host materials was evaluated using inbuilt data analysis methods, mainly by principal component analysis (PCA) and cross-validation. GC-MS analysis was conducted contemporaneously and identified an 80% similarity between healthy and infected plant material. The portable C 320 was 100% successful in discriminating known volatiles but had a low capability in differentiating healthy and infected plant substrates. The advanced devices (PEN 3/MSEM 160) successfully detected healthy and diseased samples with a high variance. The results suggest that E-noses are more sensitive and accurate in detecting changes of VOCs between healthy and infected plants compared to headspace GC-MS. The study was conducted in controlled laboratory conditions, as E-noses are highly sensitive to surrounding volatiles. Full article
(This article belongs to the Special Issue GC, MS and GC-MS Analytical Methods: Opportunities and Challenges (Second Edition))
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20 pages, 5919 KiB  
Article
First Direct Gravimetric Detection of Perfluorooctane Sulfonic Acid (PFOS) Water Contaminants, Combination with Electrical Measurements on the Same Device—Proof of Concepts
by George R. Ivanov, Tony Venelinov, Yordan G. Marinov, Georgi B. Hadjichristov, Andreas Terfort, Melinda David, Monica Florescu and Selcan Karakuş
Chemosensors 2024, 12(7), 116; https://doi.org/10.3390/chemosensors12070116 - 22 Jun 2024
Viewed by 714
Abstract
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are pollutants of concern due to their long-term persistence in the environment and human health effects. Among them, perfluorooctane sulfonic acid (PFOS) is very ubiquitous and dangerous for health. Currently, the detection levels required by the legislation can [...] Read more.
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are pollutants of concern due to their long-term persistence in the environment and human health effects. Among them, perfluorooctane sulfonic acid (PFOS) is very ubiquitous and dangerous for health. Currently, the detection levels required by the legislation can be achieved only with expensive laboratory equipment. Hence, there is a need for portable, in-field, and possibly real-time detection. Optical and electrochemical transduction mechanisms are mainly used for the chemical sensors. Here, we report the first gravimetric detection of small-sized molecules like PFOS (MW 500) dissolved in water. A 100 MHz quartz crystal microbalance (QCM) measured at the third harmonic and an even more sensitive 434 MHz two-port surface acoustic wave (SAW) resonator with gold electrodes were used as transducers. The PFOS selective sensing layer was prepared from the metal organic framework (MOF) MIL-101(Cr). Its nano-sized thickness and structure were optimized using the discreet Langmuir–Blodgett (LB) film deposition method. This is the first time that LB multilayers from bulk MOFs have been prepared. The measured frequency downshifts of around 220 kHz per 1 µmol/L of PFOS, a SAW resonator-loaded QL-factor above 2000, and reaction times in the minutes’ range are highly promising for an in-field sensor reaching the water safety directives. Additionally, we use the micrometer-sized interdigitated electrodes of the SAW resonator to strongly enhance the electrochemical impedance spectroscopy (EIS) of the PFOS contamination. Thus, for the first time, we combine the ultra-sensitive gravimetry of small molecules in a water environment with electrical measurements on a single device. This combination provides additional sensor selectivity. Control tests against a bare resonator and two similar compounds prove the concept’s viability. All measurements were performed with pocket-sized tablet-powered devices, thus making the system highly portable and field-deployable. While here we focus on one of the emerging water contaminants, this concept with a different selective coating can be used for other new contaminants. Full article
(This article belongs to the Special Issue Chemical Sensors and Analytical Methods for Environmental Monitoring)
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